Low dielectric constant organic dielectrics based on cage-like structures

ABSTRACT

A low dielectric constant material has a first backbone with an aromatic moiety and a first reactive group, and a second backbone with an aromatic moiety and a second reactive group, wherein the first and second backbones are crosslinked via the first and second reactive groups in a crosslinking reaction without an additional crosslinker, and wherein a cage structure having at least 10 atoms is covalently bound to at least one of the first and second backbone.

FIELD OF THE INVENTION

[0001] The field of the invention is low dielectric constant materials.

BACKGROUND OF THE INVENTION

[0002] Interconnectivity in integrated circuits increases withdecreasing size of functional elements and increasing complexity. Toaccommodate the growing demand of interconnections, complexconfigurations of conductors and insulators have been developed. Suchconfigurations generally consist of multiple layers of metallicconductor lines embedded in multiple layers of insulators, which arefabricated from one or several low dielectric constant materials. Thedielectric constant in such materials has a very important influence onthe performance of the integrated circuit. Insulator materials havinglow dielectric constants (i.e. below 3.0) are especially desirable,because they typically allow faster signal propagation, reducecapacitive effects and cross talk between conductor lines, and lowervoltages to drive integrated circuits.

[0003] One way of achieving low dielectric constants in the insulatormaterial is to employ materials with inherently low dielectricconstants. Generally, two different classes of low dielectric constantmaterials have been employed in recent years—inorganic oxides andorganic polymers. Inorganic oxides, which may be applied by chemicalvapor deposition or spin-on techniques, have dielectric constantsbetween about 3 and 4, and have been widely used in interconnects withdesign rule larger than 0.25 μm. However, as the dimension ofinterconnects continue to shrink, materials with even lower dielectricconstant become more desirable.

[0004] Since 1998 integrated circuits with 0.25 μm design rule have beenin production, but will be superseded by the production of the 0.18 μmgeneration ICs in 1999, and materials having dielectric constants lowerthan 3.0 are needed immediately. As the trend to even smaller designrules continues, design rules smaller than 0.18 μm are being developed,and design rules of 0.071 μm and below can be expected in just a fewgenerations, suggesting a strong need for dielectric materials withdesigned-in nanoporosity. Since air has a dielectric constant of about1.0, a major goal is to reduce the dielectric constant of nanoporousmaterials down towards a theoretical limit of 1, and several methods areknown in the art for fabricating nanoporous materials.

[0005] In some methods, the nanosized voids are generated byincorporation of hollow, nanosized spheres in the matrix material,whereby the nanosized spheres acts as a “void carriers”, which may ormay not be removed from the matrix material. For example, U.S. Pat. No.5,458,709 to Kamezaki et al., the inventors teach the use of hollowglass spheres in a material. However, the distribution of the glassspheres is typically difficult to control, and with increasingconcentration of the glass spheres, the dielectric material losesflexibility and other desirable physico-chemical properties.Furthermore, glass spheres are generally larger than 20 nm, and aretherefore not suitable for nanoporous materials where pores smaller than2 nm are desired.

[0006] To produce pores with a size substantially smaller than glassspheres, Rostoker et al. describe in U.S. Pat. No. 5,744,399 the use offullerenes as void carriers. Fullerenes are a naturally occurring formof carbon containing from 32 atoms to about 960 atoms, which is believedto have the structure of a spherical geodesic dome. The inventors mix amatrix material with fullerenes, and cure the mixture to fabricate ananoporous dielectric, wherein the fullerenes may be removed from thecured matrix. Although the pores obtained in this manner are generallyvery uniform in size, homogeneous distribution of the void carriersstill remains problematic.

[0007] In other methods, the nanosized voids are generated from acomposition comprising a thermostable matrix and a thermolabile(thermally decomposable) portion, which is either separately added tothe thermostable matrix material (physical blending approach), orbuilt-in into the matrix material (chemical grafting approach). Ingeneral, the matrix material is first cured and crosslinked at a firsttemperature T_(XL) to obtain a high T_(G) matrix, then the temperatureis raised to a second temperature T_(T) (such that T_(T)<T_(G)) tothermolyze the thermolabile portion, and postcured at a thirdtemperature (T_(C), with T_(C)<T_(G)) to form the desired nanoporousmaterial having voids corresponding in size and position to the size andposition of the thermolabile portion. Continued heating of thenanoporous material beyond T_(C) will result in further annealing andstabilization of the nanoporous material.

[0008] In a physical blending approach, a thermostable matrix is blendedwith a thermolabile portion, the blended mixture is crosslinked, and thethermolabile portion thermolyzed. The advantage of this approach is thatvariations and modifications in the thermolabile portion and thethermostable matrix are readily achieved. However, the chemical natureof both the thermolabile portion and thermostable matrix generallydetermine the usable window among T_(XL), T_(T), and T_(G) such thatT_(XL)<T_(T)<T_(G), thereby significantly limiting the choice ofavailable materials. Moreover, blending thermolabile and thermostableportions usually allows only poor control over pore size and poredistribution.

[0009] In the chemical grafting approach, a somewhat better control ofpore size and pore distribution can be achieved when thermolabileportions and thermostable portions are incorporated into a single blockcopolymer. The block copolymer is first heated to crosslink the matrix,further heated to thermolyze the thermolabile blocks, and then cured toyield the nanoporous material. Alternatively, thermostable portions andthermostable portions carrying thermolabile portions can be mixed andpolymerized to yield a copolymer, which is subsequently heated tothermolyze the thermolabile blocks. An example for this approach isshown in U.S. Pat. No. 5,776,990 to Hedrick et al. However, thesynthesis of block polymers having thermostable and thermolabileportions is relatively difficult and labor intensive, therefore addingsignificant cost. Furthermore, as the amount of thermolabile portions(i.e. porosity) increases, the nanoporous materials tend to collapsemore readily, thus limiting the total volume of voids that can beincorporated into the nanoporous material.

[0010] Although various methods are known in the art to introducenanosized voids into low dielectric constant material, all, or almostall of them have one or more than one disadvantage. Thus, there is stilla need to provide improved compositions and methods to introducenanosized voids in dielectric material.

SUMMARY OF THE INVENTION

[0011] The present invention is directed to low dielectric constantmaterials having a first backbone with an aromatic moiety and a firstreactive group, and a second backbone with an aromatic moiety and asecond reactive group, wherein the first and second backbone arecrosslinked via the first and second reactive groups in a crosslinkingreaction preferably without an additional crosslinker, and wherein acage structure having at least 10 atoms is covalently bound to at leastone of the first and second backbone.

[0012] In one aspect of the inventive subject matter first and secondbackbone are identical, preferably comprise a phenyl group, morepreferably comprise a poly(arylene ether), and most preferably comprisea substituted resorcinol, a substituted tolane, or a substituted phenolas aromatic moiety. In other preferred aspects, the first and secondreactive groups are non-identical and comprise an ethynyl moiety or atetracyclone moiety, and the crosslinking reaction is a cycloadditionreaction.

[0013] In another aspect of the inventive subject matter the cagestructure preferably comprises a substituted or unsubstitutedadamantane, or substituted or unsubstituted diamantane, wherein theadamantane or diamantane may be incorporated into the backbone, as apendent group or such that the cage structure has a tetrahedral orpolyhedral configuration.

[0014] Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

[0015]FIG. 1 is a synthetic scheme to produce a low molecular weightpolymer with pendent cage structures according to the inventive subjectmatter.

[0016]FIG. 2 is a synthetic scheme to produce another low molecularweight polymer with pendent cage structures according to the inventivesubject matter.

[0017] FIGS. 3A-D are structures of various polymers according to theinventive subject matter.

[0018] FIGS. 4A-C are synthetic schemes to produce various thermosettingmonomers according to the inventive subject matter.

[0019] FIGS. 5A-B are synthetic schemes to produce an end-cappingmolecule with pendent cage structures according to the inventive subjectmatter.

[0020]FIG. 6 is schematic structure of an exemplary low dielectricconstant material according to the inventive subject matter.

DETAILED DESCRIPTION

[0021] As used herein, the term “low dielectric constant material”refers to organic, organometallic, and inorganic materials with adielectric constant of less than 3.0. The low dielectric material istypically manufactured in the form of a thin film of less than 100 μm,however, various shapes other than a film are also contemplated underthe scope of this definition, including thick films, blocks, cylinders,spheres, etc.

[0022] As also used herein, the term “backbone” refers to a contiguouschain of atoms or moieties forming a polymeric strand that arecovalently bound such that removal of any of the atoms or moiety wouldresult in interruption of the chain.

[0023] As further used herein, the term “reactive group” refers to anyatom, functionality, or group having sufficient reactivity to form atleast one covalent bond with another reactive group in a chemicalreaction. The chemical reaction may take place between two identical, ornon-identical reactive groups, which may be located on the same or ontwo separate backbones. It is also contemplated that the reactive groupsmay react with one or more than one exogenous crosslinking molecule tocrosslink the first and second backbones. Although crosslinking withoutexogenous crosslinkers presents various advantages, including reducingthe overall number of reactive groups in the polymer, and reducing thenumber of required reaction steps, crosslinking without exogenouscrosslinkers has also a few detriments. For example, the amount ofcrosslinking functionalities can typically be no more adjusted. On theother hand, employing exogenous crosslinkers may be advantageous whenthe polymerization reaction and crosslinking reaction are chemicallyincompatible.

[0024] As still further used herein, the term “cage structure” refers toa molecule having at least 10 atoms arranged such that at least onebridge covalently connects two or more atoms of a ring system. Thebridge and/or the ring system may comprise one or more heteroatoms, andmay be aromatic, partially saturated, or unsaturated. Furthercontemplated cage structures include fullerenes, and crown ethers havingat least one bridge. For example, an adamantane or diamantane isconsidered a cage structure, while a naphthalene or an aromaticspirocompound are not considered a cage structure under the scope ofthis definition, because a naphthalene or an aromatic spirocompound donot have one, or more than one bridge.

[0025] In a preferred low dielectric constant material, the first andsecond backbone comprise a poly(arylene ether) with two pendentadamantane groups, respectively, as cage structures as shown inStructures 1A-B (only one repeating unit of the backbone is shown). Thefirst and second aromatic moieties comprise a phenyl group, and thefirst and second reactive groups are an ethynyl and a tetracyclonemoiety, respectively, which react in a Diels-Alder reaction to crosslinkthe backbones. Preferred crosslinking conditions are heating thepoly(arylene ether) backbones to a temperature of about 200° C.-250° C.for approximately 30-180 minutes. Structure 1B can be synthesized asgenerally outlined in Example 1 below.

[0026] In alternative embodiments, the backbone need not be restrictedto a poly(arylene ether), but may vary greatly depending on the desiredphysico-chemical properties of the final low dielectric constantmaterial. Consequently, when relatively high T_(G) is desired, inorganicmaterials are especially contemplated, including inorganic polymerscomprising silicate (SiO₂) and/or aluminate (Al₂O₃). In cases whereflexibility, ease of processing, or low stress/TCE, etc. is required,organic polymers are contemplated. There are many different appropriateorganic polymers, and some of the polymers may be especially suited forone purpose (e.g. low thermal coefficient of expansion), while otherpolymers may be especially suited for other purposes (e.g. superior gapfilling capability). Thus, depending on a particular application,contemplated organic backbones include aromatic polyimides, polyamides,and polyesters.

[0027] Although preferably built from low molecular weight polymers witha molecular weight of approximately 1000 to 10000, the chain length ofthe first and second polymeric backbones may vary considerably betweenfive, or less repeating units to several 10⁴ repeating units, and more.Preferred backbones are synthesized from monomers in an aromaticsubstitution reaction, and synthetic routes are shown by way of examplein FIGS. 1 and 2. It is further contemplated that alternative backbonesmay also be branched, superbranched, or crosslinked at least in part.Alternatively, the backbones may also be synthesized in-situ frommonomers. Appropriate monomers may preferably include aromaticbisphenolic compounds and difluoroaromatic compounds, which may havebetween 0 and about 20 built-in cage structures.

[0028] It is especially contemplated that appropriate monomers may havea tetrahedral structure, which are schematically depicted in Structures2A-B. In general Structure 2A, a thermosetting monomer has a cagestructure G, and at least two of the side chains R₁-R₄ comprise anaromatic portion and a reactive group, wherein at least one of thereactive groups of a first monomer reacts with at least one of thereactive group of a second monomer to produce a low dielectric constantpolymer. In general Structure 2B a cage structure, preferably anadamantane, is coupled to four aromatic portions which may participatein polymerization, and wherein R₁-R₄ may be identical or different.

[0029] When monomers with tetrahedral structure are used, the cagestructure will advantageously not only introduce a nanosized void, butalso covalently connect four backbones in a three dimensionalconfiguration. An exemplary monomer with tetrahedral structure and itssynthesis is shown in FIG. 4B. It should further be appreciated thatalternative monomers need not be limited to compounds with a substitutedor unsubstituted adamantane as a cage structure, but may also comprise asubstituted or unsubstituted diamantane, or fullerene as a cagestructure. Contemplated substituents include alkyls, aryls, halogens,and functional groups. For example, an adamantane may be substitutedwith a —CF3 group, a phenyl group, —COOH, —NO₂, or —F, —Cl, or —Br.Consequently, depending on the chemical nature of the cage structure,various numbers other than four aromatic portions may be attached to thecage structure. For example, where a relatively low degree ofcrosslinking through cage structures is desired, 1-3 aromatic portionsmay be attached to the cage structure, wherein the aromatic portions mayor may not comprise a reactive group for crosslinking. In cases wherehigher degrees of crosslinking is preferred, five and more aromaticportions may be attached to a cage structure wherein all or almost allof the aromatic portions carry one or more than one reactive group.Furthermore, it is contemplated that aromatic portions attached to acentral cage structure may carry other cage structures, wherein the cagestructures may be identical to the central cage structure, or may beentirely different. For example, contemplated monomers may have afullerene cage structure to provide a relatively high number of aromaticportions, and a diamantane in the aromatic portions. Thus, contemplatedcage structures may be covalently bound to a first and second backbone,or to more than two backbones.

[0030] With respect to the chemical nature of the aromatic portion it iscontemplated that appropriate aromatic portions comprise a phenyl group,and more preferably a phenyl group and a reactive group. For example, anaromatic portion may comprise a tolane, or a substituted tolane, whereinsubstituted tolanes may comprise additional phenyl groups covalentlybound to the tolane via carbon-carbon bonds, or carbon-non-carbon atombonds, including double and triple bonds, ether-, keto-, or estergroups.

[0031] Also contemplated are monomers that have pendent cage structures,as depicted by way of example in FIG. 4A, in which two diamantane groupsare utilized as pendent groups. It should be appreciated, however, thatpending cage structures are not limited to two diamantane structures.Contemplated alternative cage structures include single and multiplesubstituted adamantane groups, diamantane groups and fullerenes in anychemically reasonable combination. Substitutions may be introduced intothe cage structures in cases where a particular solubility, oxidativestability, or other physico-chemical properties is desired. Therefore,contemplated substitutions include halogens, alkyl, aryl, and alkenylgroups, but also functional and polar groups including esters, acidgroups, nitro and amino groups, and so forth.

[0032] It should also be appreciated that the backbones need not beidentical. In some aspects of alternative embodiments, two, or more thantwo chemically distinct backbones may be utilized to fabricate a lowdielectric constant material, as long as the alternative low dielectricconstant material comprises first and second backbones having anaromatic moiety, a reactive group, and a cage compound covalently boundto the backbone.

[0033] With respect to the reactive groups it is contemplated that manyreactive groups other than an tolanyl group and a tetracyclone group maybe employed, so long as alternative reactive groups are able tocrosslink first and second backbones without an exogenous crosslinker.For example, appropriate reactive groups include benzocyclobutenyl, andbiphenylene. In another example, a first reactive group may comprise anelectrophile, while a second reactive group may comprise a nucleophile.It is further contemplated that the number of reactive groupspredominantly depends on (a) the reactivity of the first and secondreactive group, (b) the strength of the crosslink between first andsecond backbone, and (c) the desired degree of crosslinking in the lowdielectric material. For example, when the first and second reactivegroups are sterically hindered (e.g. an ethynyl group between twoderivatized phenyl rings), a relatively high number of reactive groupsmay be needed to crosslink two backbones to a certain extent. Likewise,a high number of reactive groups may be required to achieve stablecrosslinking when relatively weak bonds such as hydrogen bonds or ionicbonds are formed between the reactive groups.

[0034] In cases where a reactive group in one backbone is capable ofreacting with an identical reactive group in another backbone, only onetype of reactive group may be needed. For example, tolanyl groupslocated on the same of two different backbones may react in anaddition-type reaction to form crosslinking structures.

[0035] It should also be appreciated that the number of reactive groupsmay influence the ratio of intermolecular to intramolecularcrosslinking. For example, a relatively high concentration of reactivegroups in first and second backbones at a relatively low concentrationof both backbones may favor intramolecular reactions. Similarly, arelatively low concentration of reactive groups in first and secondbackbones at a relatively high concentration of both backbones may favorintermolecular reactions. The balance between intra- and intermolecularreactions may also be influenced by the distribution of non-identicalreactive groups between the backbones. When an intermolecular reactionis desired, one type of reactive group may be placed on the firstbackbone, while another type of reactive group may be positioned on thesecond backbone. Furthermore, additional third and fourth reactivegroups may be employed when sequential crosslinking at differentconditions is desired (e.g. two different temperatures).

[0036] The reactive groups of preferred backbones react in anaddition-type reaction, however, depending on the chemical nature ofalternative reactive groups, many other reactions are also contemplated,including nucleophilic and electrophilic substitutions, or eliminations,radical reactions, etc. Further alternative reactions may also includethe formation of non-covalent bonds, such as electrostatic bonds,hydrophobic bonds, ionic bonds and hydrogen bonds. Thus, crosslinkingthe first and second backbone may occur via a covalent or non-covalentbond formed between identical or non-identical reactive groups, whichmay be located on the same or two backbones.

[0037] In further aspects of alternative embodiments, the cage structuremay comprise structures other than an adamantane, including adiamantane, bridged crown ethers, or fullerenes, as long as alternativecage structures have 10 or more atoms. The selection of appropriate cagestructures is determined by the desired degree of steric demand of thecage structure. If relatively small cage structures are preferred, asingle adamantane, or diamantane group may be sufficient. Exemplarystructures of backbones including adamantane and diamantane groups areshown in FIGS. 3A and 3B. Large cage structures may comprise fullerenes.It should also be appreciated that alternative backbones need not belimited to a single type of cage structure. Appropriate backbones mayalso include 2-5, and more non-identical cage structures. For example,fullerenes may be added to one or both ends of a polymeric backbone,while diamantane groups are placed in the other parts of the backbone.Further contemplated are derivatized, or multiple cage structures,including oligomerized and polymerized cage structures, where evenlarger cage structures are desired. The chemical composition of the cagestructures need not be limited to carbon atoms, and it should beappreciated that alternative cage structures may have atoms other thancarbon atoms (i.e. heteroatoms), whereby contemplated heteroatoms mayinclude N, O, P, S, B, etc.

[0038] With respect to the position of the cage structure it iscontemplated that the cage structure may be connected to the backbone invarious locations. For example, when it is desirable to mask terminalfunctional groups in the backbone, or to terminate a polymerizationreaction forming a backbone, the cage structure may be employed as anend-cap. Exemplary structures of end-caps are shown in FIGS. 5A and B.In other cases where large amounts of a cage structure are desired, itis contemplated that the cage structures are pendent structurescovalently connected to the backbone. The position of the covalentconnection may vary, and mainly depends on the chemical make-up of thebackbone and the cage structure. Thus, appropriate covalent connectionsmay involve a linker molecule, or a functional group, while otherconnections may be a single or double bond. When the cage group is apendent group it is especially contemplated that more than one backbonemay be connected to the cage structure. For example, a single cagestructure may connect 2-3, and more backbones. Alternatively, it iscontemplated that the cage group may be an integral part of thebackbone.

[0039] It is still further contemplated that alternative low dielectricconstant material may also comprise additional components. For example,where the low dielectric constant material is exposed to mechanicalstress, softeners or other protective agents may be added. In othercases where the dielectric material is placed on a smooth surface,adhesion promoters may advantageously employed. In still other cases theaddition of detergents or antifoam agents may be desirable.

[0040] Turning now to FIG. 6, an exemplary low dielectric constantmaterial is shown in which a first backbone 10 is crosslinked to asecond backbone 20 via a first reactive group 15 and a second reactivegroup 25, wherein the crosslinking results in a covalent bond 50. Bothbackbones have at least one aromatic moiety (not shown), respectively. Aplurality of pendent cage structures 30 are covalently bound to thefirst and second backbones, and the first backbone 10 further has aterminal cage group 32. The terminal cage group 32, and at least one ofthe pendent cage groups 30 carries at least one substituent R 40,wherein substituent 40 may be a halogen, alkyl, or aryl group. Each ofthe cage structures comprises at least 10 atoms.

EXAMPLES

[0041] The following examples describe exemplary synthetic routes forproduction of backbones having cage-like structures.

Example 1 Synthesis of 4,6-bis(adamantyl)resorcinol

[0042] Into a 250-mL 3-neck flask, equipped with nitrogen inlet,thermocouple and condenser, were added resorcinol (11.00 g, 100.0 mMol),bromoadmantane (44.02 g, 205.1 mMol) and toluene (150 mL). The mixturewas heated to 110° C. and became a clear solution. The reaction wasallowed to continue for 48 h, at which time TLC showed that all theresorcinol had disappeared. The solvent was removed and the solid wascrystallized from hexanes (150 mL). The disubstituted product wasobtained in 66.8% yield (25.26 g) as a white solid. Another 5.10 gproduct was obtained by silica gel column chromatography of theconcentrated mother liquor after the first crop. The total yield of theproduct was 80.3%. Characterization of the product was by proton NMR,HPLC, FTIR and MS.

Incorporation of 4,6-bis(adamantyl)resorcinol into a poly(arylene ether)Backbone

[0043] In a 250-mL 3-neck flask, equipped with a nitrogen inlet,thermocouple and Dean-Stark trap, were added bis(adamantyl)resorcinol(7.024 g, 18.57 mMol), FBZT (5.907 g, 18.57 mMol), potassium carbonate(5.203 g, 36.89 mMol) and DMAC (50 mL), toluene (25 mL). The reactionmixture was heated to 135° C. to produce a clear solution. The reactionwas continued for 1 h at this temperature and the temperature was raisedto 165° C. by removing some of the toluene. The course of polymerizationwas monitored by GPC. At M_(w)=22,000, the reaction was stopped. Another50-mL portion of DMAC was added to the reaction flask. The solid wasfiltered at room temperature, and was extracted with hot dichloromethane(2×150 mL). Methanol (150 mL) was added to the solution to precipitate awhite solid, which was isolated by filtration. The yield was 65.8%(8.511 g). The solid was dissolved in THF (150 mL) and methanol (300 mL)was added to the solution slowly. The precipitated white solid wasisolated by filtration and dried in vacuo at 90° C.

Example 3

[0044]

[0045] The synthetic procedure for backbone 1 follows the procedure asdescribed in Example 2, but employs 4,4′-difluorotolane as the difluorocompound.

Example 4 Contemplated Alternative Backbones

[0046] The following structures are contemplated exemplary backbonesthat can be fabricated according to the general synthetic procedure inExamples 1 and 2.

Example 5

[0047] This example demonstrates an exemplary synthesis for athermosetting monomer as depicted in FIG. 4B according to the inventivesubject matter.

Synthesis of 1,3,5,7-tetrabromoadamantane

[0048] Tetrabromoadamantane synthesis started from commerciallyavailable adamantane and followed the synthetic procedures as describedin G. P. Sollott and E. E. Gilbert, J. Org. Chem., 45, 5405-5408 (1980),B. Schartel, V. Stümpflin, J. Wendling, J. H. Wendorff, W. Heitz, and R.Neuhaus, Colloid Polym. Sci., 274, 911-919 (1996), or A. P. Khardin, I.A. Novakov, and S. S. Radchenko, Zh. Org. Chem., 9, 435 (1972).Quantities of up to 150 g per batch were routinely synthesized.

Synthesis of 1,3,5,7-tetrakis(3/4-bromophenyl)adamantane

[0049] 1,3,5,7-tetrakis(3/4-bromophenyl)adamantane was synthesized from1,3,5,7-tetrabromoadamantane following a procedure as describedelsewhere (V. R. Reichert and L. J. Mathias, Macromolecules, 27,7015-7023 (1994), V. R. Reichert, Ph. D. Dissertation, “Investigation ofderivatives and polymers of 1,3,5,7-tetraphenyladamantane,” Universityof Southern Mississippi, 1994). LC-MS was used to identify thecomponents of the isomeric mixture after the first synthesis. Treatingthe reaction product with fresh AlBr₃ catalyst favored the compositionof the isomeric mixture kinetically the one that was enriched in Ph4Br4isomer.

Synthesis of 1,3,5,7-tetrakis(3/4-tolanyl)adamantane

[0050] 1,3,5,7-tetrakis(3/4-tolanyl)adamantane was synthesized from1,3,5,7-tetrakis(3/4-bromophenyl)adamantane by reacting1,3,5,7-tetrakis(3/4-bromophenyl)adamantane in triethylamine with anabout nine-fold molar excess of phenylacetylene in the presence of Pdcatalyst dichlorobis(triphenylphosphine)palladium[II] and copper[I]iodide for 4 hours at 80° C.

Example 6

[0051] Adamantanyl endcapped monomers as shown in FIGS. 5A and 5B weresynthesized as described in C. M. Lewis, L. J. Mathias, N. Wiegal, ACSPolymer Preprints, 36(2), 140 (1995).

[0052] Thus, specific embodiments, applications, and methods forproducing low dielectric constant dielectrics having cage-likestructures have been disclosed. It should be apparent, however, to thoseskilled in the art that many more modifications besides those alreadydescribed are possible without departing from the inventive conceptsherein. The inventive subject matter, therefore, is not to be restrictedexcept in the spirit of the appended claims. Moreover, in interpretingboth the specification and the claims, all terms should be interpretedin the broadest possible manner consistent with the context. Inparticular, the terms “comprises” and “comprising” should be interpretedas referring to elements, components, or steps in a non-exclusivemanner, indicating that the referenced elements, components, or stepsmay be present, or utilized, or combined with other elements,components, or steps that are not expressly referenced.

What is claimed is:
 1. A low dielectric constant material, comprising: afirst backbone having a first aromatic moiety and a first reactivegroup; a second backbone having a second aromatic moiety and a secondreactive group, wherein the first and second backbones are crosslinkedvia the first and second reactive groups in a crosslinking reaction; anda cage structure covalently bound to at least one of the first andsecond backbones, wherein the cage structure comprises at least 10atoms.
 2. The low dielectric constant material of claim 1 wherein thecrosslinking reaction takes place without an exogenous crosslinker. 3.The low dielectric constant material of claim 2 wherein the aromaticmoiety comprises a phenyl.
 4. The low dielectric constant material ofclaim 2 wherein the aromatic moiety comprises an arylene ether.
 5. Thelow dielectric constant material of claim 2 wherein the first backbonecomprises a poly(arylene ether).
 6. The low dielectric constant materialof claim 2 wherein the first reactive groups comprises an electrophile.7. The low dielectric constant material of claim 2 wherein the firstreactive groups comprises an tetracyclone.
 8. The low dielectricconstant material of claim 2 wherein the second reactive groupscomprises a nucleophile.
 9. The low dielectric constant material ofclaim 2 wherein the second reactive groups comprises a tolanyl group.10. The low dielectric constant material of claim 2 wherein the firstand second reactive groups are identical.
 11. The low dielectricconstant material of claim 2 wherein the reaction is a cycloaddition.12. The low dielectric constant material of claim 11 wherein thecycloaddition is a Diels-Alder reaction.
 13. The low dielectric constantmaterial of claim 2 wherein the cage structure comprises at least onecarbon atom.
 14. The low dielectric constant material of claim 2 whereinthe cage structure comprises at least one of an adamantane and adiamantane.
 15. The low dielectric constant material of claim 2, whereinthe cage structure is substituted with a substituent.
 16. The lowdielectric constant material of claim 2, wherein the substituent isselected from the group consisting of a halogen, an alkyl, and an aryl.17. The low dielectric constant material of claim 2 wherein the cagestructure is covalently bound to the first and the second backbone. 18.The low dielectric constant material of claim 2 wherein the cagestructure is covalently bound to at least one of the termini of thefirst and the second backbone.
 19. A low dielectric constant polymerhaving the structure:

wherein B is

with n=1-3, and wherein x=1-10³, wherein R is

and Ar is


20. A low dielectric constant polymer having the structure:

wherein n=1-10³.
 21. A thermosetting monomer having the structure:

wherein G is a cage structure, and wherein at least two of R₁-R₄comprise an aromatic portion and a reactive group, respectively; andwherein at least one of the reactive groups of a first monomer reactswith at least one of the reactive group of a second monomer to produce alow dielectric constant polymer.